This invention relates in general to voltage regulators in integrated circuit (IC) technology and, in particular, to an IC regulator which is highly advantageous in supplying a constant current source to a current mode logic device used in high speed digital logic systems.
IC voltage regulators capable of providing a zero temperature coefficient regulated output voltage have already been developed. Such regulators have also been developed to supply a constant output voltage for logic circuits within a limited range of variations of the supply voltage. One manner of providing the constant output voltage in such regulators is to use a PNP transistor to provide the constant current in the shunt feedback transistor of the regulator. However, the disadvantage in such a system is the dependency on the absolute characteristics of the PNP transistor, which limited the voltage supply variation range because of the current limitations on the vertical PNP.
Another approach to making the prior art regulators more responsive to a wider range of fluctuations of supply voltage has been to add a feedback supply amplifier coupled to the shunt transistor which senses the changes in supply voltage and adds or subtracts from the collector current flowing through the shunt transistor so as to maintain the base emitter voltage of the shunt transistor (V.sub.BE) constant; the shunt transistor being matched to the input transistor of a current mode logic device to which the regulator was coupled.
This invention is an improvement in voltage regulators by approaching the compensation for fluctuations in the voltage supply differently from the prior art regulators in that the shunt transistor is effectively eliminated from the regulator insofaras attempting to maintain the current through the shunt transistor constant over variations of supply voltage and performance of the regulator is dependent only on relative matching of the devices thereon.
Accordingly, it is an object to this invention to provide an IC regulator which is fully temperature and supply voltage compensated so as to be responsive to a wide range of variations in supply voltage.
It is a more specific object to this invention to provide an IC regulator which is fully temperature and supply voltage compensated yet does not depend on maintaining the current flow constant in the shunt transistor as in the prior art regulators.